JPH02223955A - electrophotographic photoreceptor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an electrophotographic photoreceptor, and more particularly to an electrophotographic photoreceptor with excellent sensitivity and potential stability.

[Conventional technology]

Conventionally, electrophotographic photoreceptors having photosensitive layers mainly composed of inorganic compounds such as selenium, zinc oxide, and cadmium sulfide have been widely used, but these inorganic photoreceptors have poor thermal stability, moisture resistance, It is not necessarily satisfactory in terms of toxicity, etc.

On the other hand, electrophotographic photoreceptors with a photosensitive layer mainly composed of organic compounds have many advantages over inorganic ones, such as ease of film formation, non-pollution, and ease of manufacture. In particular, a layered photoconductor consisting of a layer containing a substance that generates charges when irradiated with light (charge generation layer) and a layer containing a substance that transports charges (charge transfer layer) is different from conventional photoconductors. There are some that have been put into practical use because they have better sensitivity and stable charging ability.

For example, JP-A-59-33445 and JP-A-60-11 disclose photoreceptors using azo pigments as charge-generating substances.
Publication No. 1249 and the like are publicly known. However, photoreceptors using these azo pigments as charge-generating substances are not necessarily satisfactory in terms of sensitivity, residual potential, or stability during repeated use (in addition, the selection range of charge-transporting substances is limited, etc.). It does not fully satisfy the wide range of requirements of electrophotographic processes.

[Problem that the invention seeks to solve]

An object of the present invention is to provide an electrophotographic photoreceptor with high sensitivity and high durability.

[Means for solving problems]

That is, the present invention is an electrophotographic photoreceptor having a photosensitive layer on a conductive support, characterized in that the photosensitive layer contains a compound having a structure represented by the following general formula (1) or (2). It is an electrophotographic photoreceptor.

In general formulas (1) and (2), A1 and A3 represent an alkyl group, an aralkyl group, an aromatic group, or a heterocycle which may have a substituent. A2 represents a hydrogen atom or an alkyl group, an aralkyl group, an aromatic group, or a heterocyclic group which may have a substituent. Examples of the alkyl group include methyl, ethyl, propyl, butyl, and the like. Examples of the aralkyl group include benzyl, phenethyl, naphthylmethyl, and the like. Examples of aromatic groups include aromatic monocyclic groups such as benzene, naphthalene, anthracene, phenanthrene, pyrene, azulene, indene, and fluorene, aromatic fused polycyclic groups, or two or more of these monocycles and fused polycyclic groups. A ring assembly group in which the ring systems of are directly bonded through a double bond, etc., penzophein, fluorenone.

Aromatic ketone groups and their sulfur derivatives (e.g. thiobenzophenone) groups such as pensuanthrone, indanone, suberenone, dicyanomethylene derivative groups, aromatic quinone groups and their sulfur derivatives such as benzoquinone, naphthoquinone, anthraquinone, phenanthrenequinone, pyrenequinone group, dicyanomethylene derivative group, and the like.

Examples of heterocyclic groups include furan, thiophene, pyrrole, oxazole, thiazole, and imidazole.

Pyrazole, pyridine, pyrazine, piperazine.

Benzofuran, benzothiophene, indole.

Benzoxazole, benzthiazole, dibenzofuran, dibenzothiophene, carbazole.

Phenazine, phenooxazine, phenothiazine.

Thianthrene, acridonke This heterocyclic group or a heterocyclic group fused with a benzene ring or an aromatic condensed polycycle, or a ring system in which two or more of these monocycles or condensed polycycles are directly bonded with a double bond, etc. Examples include ring aggregation groups.

Examples of the substituents that the above alkyl groups, aralkyl groups, aromatic groups and heterocyclic groups may have include halogen groups such as fluorine, chlorine, bromine and iodine, alkyl groups such as methyl, ethyl, propyl and butyl, and methoxy , ethoxy, phenoxy and other alkoxy groups, nitro groups, cyano groups, dimethylamino, diethylamino, diphenylamino, dibenzylamino, morpholino, piperidino, pyrrolidino and other substituted amino groups.

In general formulas (1) and (2), A1 and A2 may be the same or different, and A.

and A2 may jointly form a ring. n is l.

Represents an integer of 2 or 3. Furthermore, in the present invention, in general formulas (1) and (2), when A and A2 are electron donating moieties, A3 is an electron accepting moiety, and when A and A2 are electron accepting moieties, A3 is an electron accepting moiety. is preferably an electron-donating moiety. In particular, good properties are provided when there is an electron-donating moiety on the N side of the )C=N- bond and an electron-accepting moiety on the C side.

Examples of electron-donating moieties include electron-donating aromatic monocyclic groups such as benzene, naphthalene, anthracene, phenanthrene, indene, and fluorene having electron-donating substituents, and pyrene which may have electron-donating substituents. or an electron-donating aromatic condensed polycyclic group, an electron-donating aromatic amine group such as triphenylamine, diphenylamine, diphenylmethylamine, which may have an electron-donating substituent;
Furan, thiophene, pyrrole, oxazole, thiazole, imidazole, pyridine, pyrazine, acridine, phenazine, benzofuran, benzothiophene, dibenzofuran, dibenzothiophene, benzoxazole, benzthiazole, thianthrene, phenoxazine, phenothiazine having an electron-donating substituent Electron-donating heteromonocyclic groups such as indole, carbazole, iminodibenzyl, tetrathiafulvalene, dibenzotetrathiafulvalene, which may have an electron-donating substituent, benzene ring, aromatic condensed polycyclic ring and condensed size. Examples include an electron-donating fused heterocyclic group, or an electron-donating substituent in which two or more ring systems of these monocycles or condensed rings are directly bonded via a double bond or the like.

Examples of electron-donating substituents include methyl.

Alkyl groups such as ethyl, propyl, butyl, aryl groups such as phenyl and naphthyl, and benzyl.

Examples include aralkyl groups such as phenethyl, alkoxy groups such as methoxy and ethoxy, and substituted amino groups such as dimethylamino, diphenylamino and morpholino.

On the other hand, the electron-accepting moiety includes, for example, an electron-accepting aromatic monocyclic group or an electron-accepting aromatic condensed polycyclic group such as benzene, naphthalene, anthracene, phenanthrene, indene, and fluorene having an electron-accepting substituent; Electron-accepting aromatic ketone groups such as benzophenone, fluorenone, and benzanthrone, which may have an electron-accepting substituent, and their dicyanomethylene derivative groups, electron-accepting aromatic thioketone groups, benzoquinone, naphthoquinone, anthraquinone, pyrenequinone, etc. electron-accepting aromatic quinone groups and their dicyanomethylene derivative groups, furans having electron-accepting substituents.

Electron-accepting heteromonocycles or benzenes such as thiophene, pyrrole, oxazole, thiazole, imidazole, pyridine, pyrazine, acridine, phenazine, benzofuran, benzothiophene, dibenzofuran, dibenzothiophene, benzoxazole, benzthiazole, thianthrene, phenooxazine, phenothiazine Electron-accepting condensed heterocyclic groups condensed with rings or aromatic condensed polycycles, and electron-accepting substituents in which two or more of these monocycles or condensed rings are directly bonded via a double bond, etc. Examples include.

An example of an electron-accepting substituent is fluorine.

Examples include halogen groups such as chlorine, bromine, and iodine, nitro groups, and cyano groups.

In addition, A2 is particularly preferably a hydrogen atom among the above-mentioned examples.

In electrophotographic photoreceptors, in order to achieve longer wavelength spectral sensitivity, it is necessary to lengthen the absorption spectrum of the charge generating material, and it is necessary to lengthen the wavelength by expanding the π-electron conjugated system and increasing intermolecular interactions. It has been known. Regarding the substituent effect of substituted azobenzene-based compounds, it has been reported that the absorption spectrum becomes longer wavelength as the electron-donating or electron-accepting property of the substituent increases, but this is due to the π-electron conjugation of azobenzene. It is thought that this is due to intramolecular charge transfer interactions via the azo group (-N=N-), which is a chain [J. Griffiths, “Color and
Construction of Organic Molecules Academic Press London, 1976], by combining a material with large electron donating property and a material with large electron accepting property, a significantly longer wavelength is expected.

On the other hand, in an electrophotographic photoreceptor, in order to improve sensitivity, it is necessary to increase the generation efficiency of charge carriers, and carrier dissociation efficiency is cited as one of the factors governing the generation efficiency of charge carriers. It has been reported for phthalocyanine compounds that the local electric field created by ion-adsorbed gas has a large effect on carrier dissociation efficiency.
It is believed that local electric fields based on charge transfer interactions between electron-donating and electron-accepting substances (page 216) also promote the generation of charge carriers.

From the above-mentioned viewpoint, the photoconductive compound of the present invention is characterized in that the electron-donating moiety and the electron-accepting moiety interact through the C=N-bond, and that the electron-donating moiety and the electron-accepting moiety interact intermolecularly in the crystalline state. It gives good properties when the sexual parts interact through charge transfer.

General formula (1) and The front side is shown below.

A I+C=N As ] (n=1.2.3) (n=1.21 a) Compounds represented by general formulas (1) and (2) are represented by the following reaction formula. As described above, it can be easily synthesized by dehydration condensation reaction of the corresponding aromatic amine and aromatic aldehyde or aromatic ketone in the presence of an acid or base catalyst.

The electrophotographic photoreceptor of the present invention has a photosensitive layer containing a compound represented by the above general formula (1) or (2) on a conductive support.

The photosensitive layer may have any form, but the photosensitive layer containing the compound represented by the general formula (1) or (2) is used as a charge generation layer, and the charge transporting layer containing a charge transporting substance is used as a charge generation layer. A functionally separated type photosensitive layer in which layers are laminated is particularly preferred.

The charge generation layer can be formed by coating a coating solution in which the above-mentioned compound is dispersed together with a binder resin in a suitable solvent on a conductive support by a known method, and the film thickness thereof is, for example, 5 μm. Below, preferably 0.0
A thin film layer of 1 μm to 1 μm is desirable.

The binder resin used in this case is selected from a wide range of insulating resins or organic photoconductive polymers, including polyvinyl butyral, polyvinylbenzal, polyarylate, polycarbonate, polyester, phenoxy resin, cellulose resin, acrylic resin, urethane resin. etc., and the amount used is 80% in terms of content in the charge generation layer.
It is not more than 40% by weight, preferably not more than 40% by weight.

Further, the solvent used is preferably selected from those that dissolve the resin described above but do not dissolve the charge transport layer or undercoat layer described below. Specifically, tetrahydrofuran, l, 4-
Ethers such as dioxane; ketones such as cyclohexanone and methyl ethyl ketone; amides such as N,N-dimethylformamide; esters such as methyl acetate and ethyl acetate; aromatics such as toluene, xylene, and monochlorobenzene; methanol, Ethanol, 2-
Examples include alcohols such as pronoknol; aliphatic halogenated hydrocarbons such as chloroform and methylene chloride.

The charge transport layer is laminated above or below the charge generation layer and has the function of receiving charge carriers from the charge generation layer in the presence of an electric field and transporting them to the surface. The charge transport layer is formed by dissolving a charge transport material in a solvent together with a suitable binder resin as required and applying the solution. The film thickness is generally 5 μm to 40 μm, especially 15 μm to 30 μm.
μm is preferred.

Charge transport materials include electron transport materials and hole transport materials. Examples of electron transport materials include 2,4,7-dolinitrofluorenone, 2,4,5,7-titranitrofluorenone, chloranil, and tetracyanoquinodifluorenone. Examples include electron-withdrawing substances such as methane and polymerized materials of these electron-withdrawing substances.

Examples of hole transport substances include polycyclic aromatic compounds such as pyrene and anthracene; carbazole, indole, imidazole, oxazole, thiazole, oxadiazole,
Heterocyclic compounds such as pyrazole, pyrazoline, thiadiazole, triazole; hydrazone compounds such as p-diethylaminobenzaldehyde N, N-diphenylhydrazone, N,N-diphenylhydrazino-3-methylidene-9-ethylcarbazole; α-phenyl -4'
-N, N diphenylaminostilbene, 5-(4-(di-p-tolylamino)benzylidene]-5H-dibenzo(a, d) cycloheptene and other styryl compounds;
benzidine-based compounds; triarylmethane-based compounds; triphenylamine, or polymers having a group consisting of these compounds in the main chain or side chain (e.g. poly-N-
(vinylcarbazole, polyvinylanthracene, etc.).

In addition to these organic charge transport materials, inorganic materials such as selenium, selenium-tellurium, and amorphous silicon can also be used.

Further, these charge transport substances can be used alone or in combination of two or more.

When the charge transport material does not have film-forming properties, an appropriate binder resin can be used, and specifically, acrylic resin, polyarylate, polyester, polycarbonate, polystyrene, acrylonitrile-styrene copolymer, polysulfone, polyacrylamide, Examples include insulating resins such as polyamide and chlorinated rubber, and organic photoconductive polymers such as poly-N-vinylcarbazole and polyvinylanthracene.

As the conductive support, for example, aluminum, aluminum alloy, copper, zinc, stainless steel, titanium, etc. can be used. In addition, plastics coated with these metals by vacuum evaporation, conductive particles (e.g. carbon black, silver particles, etc.) coated on a plastic or metal support with an appropriate binder, or conductive particles coated on a plastic or metal support. Impregnated plastic or paper can be used.

An undercoat layer having barrier and adhesive functions can also be provided between the conductive support and the photosensitive layer.

The thickness of the undercoat layer is 5 μm or less, preferably 0.1 μm or more.
3 μm is appropriate. The undercoat layer is made of casein, polyvinyl alcohol, nitrocellulose, polyamide (nylon 6, nylon 66, nylon 610, copolymerized nylon,
N-alkoxymethylated nylon, etc.), polyurethane, aluminum oxide, etc.

Another specific example of the present invention is an electrophotographic photoreceptor containing the above-mentioned compound and a charge transport material in the same layer. At this time, poly-N-
Charge transfer complexes consisting of vinyl carbazole and trinitrofluorenone can also be used.

The electrophotographic photoreceptor of this example can be formed by coating and drying a solution in which the above-mentioned compound and charge transport material are dispersed in a suitable resin solution.

The general formula used in any electrophotographic photoreceptor (
The crystal form of the compound represented by formula (1) or (2) may be crystalline or amorphous, and if necessary, the compound represented by general formula (1) or (2) may be combined with two It is also possible to use a combination of more than one type or a combination with a known charge generating substance.

The electrophotographic photoreceptor of the present invention can be used not only in electrophotographic copying machines but also in a wide range of electrophotographic application fields such as laser beam printers, CRT printers, LED printers, liquid crystal printers, and laser engraving.

A solution prepared by dissolving 5 g of methoxymethylated nylon resin (number average molecular weight 32,000) and alcohol-soluble copolymerized nylon resin (number average molecular weight 29,000) 10 g in 95 g of methanol was applied onto the support IKP aluminum substrate using a Mayer bar, and the film was dried. A subbing layer having a thickness of 1 μm was provided.

Next, 15 g of the above-exemplified compound NaA was added to 95 g of cyclohexanone with butyral resin (butyralization degree: 63 mol%).
) was added to the dissolved solution and dispersed for 20 hours using a sand mill. This dispersion was applied onto the previously formed undercoat layer using a Mayer bar to form a charge generation layer so that the film thickness after drying was 0.2 μm.

Next, 5 g of a hydrazone compound represented by the following structural formula and polymethyl methacrylate resin (number average molecular weight 1,100,000) were dissolved in 40 g of monochlorobenzene, and this was applied onto the charge generation layer using a Mayer bar and dried to form a charge of 20 μm. A transport layer was formed, and the photoreceptor of Example 1 was produced.

Photoreceptors corresponding to Examples 2 to 47 were similarly prepared using other exemplified compounds in place of compound Na A-1.

The electrophotographic photoreceptor thus prepared was tested using an electrostatic copying paper tester (Model SP-42) manufactured by Kawaguchi Electric ■.
8), the sample was negatively charged with a corona discharge of 15 KV, left in the dark for 1 second, and then exposed to light using a halogen lamp at an illuminance of 10 lux to evaluate charging characteristics. As charging characteristics, the surface potential v0 and the exposure amount E% required for the surface potential to attenuate outward after being left in a dark place were measured.

The results are shown in Tables 1 and 2.

Using the apparatus shown in Example 1, Example 4, 9゜17.
26. The electrophotographic photoreceptor prepared in 37 and 45 was
It was charged to 00V and the exposure amount (8%: μJ/crrf) required for the potential to attenuate by half was measured. As a light source, an aluminum/gallium/silicon semiconductor laser (oscillation wavelength: 780 nm) was used. The results are shown in Table 3.

Table 3 These results show that the electrophotographic photoreceptor of the present invention has sufficient sensitivity even in the oscillation wavelength range of a semiconductor laser.

The electrophotographic photoreceptor prepared in Example 3 was assembled into an electrophotographic device equipped with a -6.5 KV corona charger, an exposure optical system, a developer, a transfer charger, a static elimination exposure optical system, and a cleaner. Attached to the cylinder of the copy machine.

The initial dark potential Vo and bright potential VL are each 700V.
, was set at around -200V, and the dark potential and bright potential were measured after repeated use 5000 times.

The photoreceptors prepared in Examples 22 and 45 were similarly evaluated, and the results are shown in Table 4.

Table 4 A polyvinyl alcohol undercoat layer having a thickness of 0.5 μm was formed on the aluminum surface of an aluminum vapor-deposited polyethylene terephthalate film. A dispersion of the compound used in Example 3 was applied thereon using a Mayer bar and dried to form a charge generation layer having a thickness of 0.2 μm.

Next, a solution prepared by dissolving 5 g of a styryl compound represented by the following structural formula and 5 g of a polycarbonate resin (number average molecular weight 55,000) in 40 g of tetrahydrofuran was applied onto the charge generation layer and dried.
A charge transport layer having a thickness of 20 μm was formed.

The charging characteristics and durability characteristics of the photoreceptor thus prepared were measured by the same method as in Examples 1 and 52.

The results are shown below.

Note that a negative sign in the potential variation amount (Δ■) represents a decrease in the absolute value of the potential, and a positive sign represents an increase.

Vo: 705 (V) Ey2: 2,1
(Iux fist 5ec) ΔVo: 10 (V) Δv
t,: 10 (V) Support 1'' A photoreceptor was prepared by coating the charge generation layer and charge transport layer of the photoreceptor prepared in Example 57 in the reverse order, and the charging characteristics were determined in the same manner as in Example 1. evaluated. However, the charging was positive.

V6: 690 (+V) E'7/
2: 3.5 (1ux6sec) K difference [5 g of 2.4.7 trinitro-9-fluorenone and poly-4,4'-dioxydiphenyl-2,2'- Propane carbonate (
molecular weight 300,000) 5g to 50% tetrahydrofuran
Apply the solution dissolved in g with a Mayer bar and dry to a film thickness of 1
A charge transport layer of 8 μm was formed.

The charging characteristics of the electrophotographic photoreceptor thus prepared were evaluated in the same manner as in Example 1. However, the charging was positive.

Vo: 680 (+V) E'/2: 3
．． 9 (Iux・5ec) Circle 11" Add 0.5g of the above-mentioned compound to 9.5g of cyclohexanone
It was also dispersed in a paint shaker for 5 hours.

A solution prepared by dissolving 5 g of the charge transport material used in Example 1 and 5 g of polycarbonate resin in 40 g of tetrahydrofuran was added to the mixture, and the mixture was further shaken for 1 hour. The coating solution thus prepared was applied onto an aluminum substrate using a Mayer bar and dried to form a photosensitive layer having a thickness of 20 μm.

The charging characteristics of the thus produced electrophotographic photoreceptor were evaluated in the same manner as in Example 1. However, the charging was positive.

V□: 690 (10V) E'/2
: 4.6 (lvnc-sec) [Effects of the Invention] As described above, the electrophotographic photoreceptor of the present invention has increased intramolecular and intermolecular interactions, and has excellent sensitivity and potential stability during repeated use. characteristics can be obtained.

Claims (1)

[Claims] (1) An electrophotographic photoreceptor having a photosensitive layer on a conductive support, characterized in that the photosensitive layer contains a compound having a structure represented by the following general formula (1) or (2). body. ▲There are mathematical formulas, chemical formulas, tables, etc.▼(1) ▲There are mathematical formulas, chemical formulas, tables, etc.▼(2) (In the formula, A_1 and A_3 are alkyl groups, aralkyl groups, aromatic groups that may have substituents. group or a heterocyclic group. A_2 represents a hydrogen atom or an alkyl group, an aralkyl group, an aromatic group, or a heterocyclic group which may have a substituent. Here, A_1 and A_2 may be the same or different. (Also, A_1 and A_2 may jointly form a ring. n represents an integer of 1, 2 or 3.) (2) In general formulas (1) and (2),
A_3 when A_1 and A_2 are electron donating moieties
2. The electrophotographic photoreceptor according to claim 1, wherein is an electron-accepting portion, and when A_1 and A_2 are electron-accepting portions, A_3 is an electron-donating portion.